This invention relates to composite membranes and to processes for their preparation and use for separating gases.
Ultrafiltration and microfiltration membranes made by coating certain acrylic latexes on a porous support (e.g. a Supor 200 membrane) are known from the article by Steve Jons et al entitled “Porous latex composite membranes: fabrication and properties”, published in the Journal of Membrane Science, Volume 155, Issue 1, 31 Mar. 1999, Pages 79-99. These membranes were used for the filtration of cherry juice. The acrylic latexes used by Jons et al did not contain oxyethylene groups.
In the later work of Ramakrishnan et al, further composite microfiltration and ultrafiltration membranes were prepared by applying latexes to porous supports such as Supor 200 (see Journal of Membrane Science, Volume 231, Issues 1-2, 1 Mar. 2004, Pages 57-70).
JP08024602 discloses gas separation composite membranes comprising a hydrophilic polymer and a hollow fibre support. The membranes however do not have a particularly good gas flux in combination with a high selectivity. The results in this publication suggest that increasing the gas flux of the support will reduce the CO2 flux of the composite membrane.
U.S. Pat. No. 5,556,449 discloses membranes based on a polyether polyamide copolymer layer on a polyvinylidene fluoride support. However no high gas fluxes are reported.
There exists a need for membranes which are capable of separating gases quickly and are selective, distinguishing between different gases; especially between CO2 and N2. For economic feasibility gas separation membranes exhibiting a high gas flux are especially preferred. For membranes separating CO2 from N2 a CO2 flux of at least 0.3×10−6 m3/m2·s·kPa, preferably at least 0.4×10−6 m3/m2·s·kPa, most preferably at least 1.0×106 m3/m2·s·kPa, is preferred in combination with at least acceptable selectivity values.